Refining of aluminum



June 16,V 1964 J. P. MCGEER REFINING oF ALUMINUM Filed Aug. 4, 1961 m lwn m.

1n s Asoon.. .Q ons MEQ ATTO/@MEMS United States Patent O 3,137,567 REFENING F ALUMINUM v James P. l/icGeer, Arvida, Quebec, Canada, assigner to Aluminium Laboratories Limited, Montreai, Quebec, Canada, a corporation ot Canada Filed Aug. 4, 19ml, Ser. No. 129,372 ll Claims. (Ci. i-63) This invention relates to aluminum. More particularly, this invention relates to the preparation of substantially pure aluminum from aluminum alloys wherein alurninum comprises a major or a minor, but substantial, portion thereof. Still more particularly, this invention relates to the production of substantially pure aluminum from carbothermic aluminum alloys, i.e. aluminum alloy or aluminum-containing metal prepared by reducing aluminous material, e.g. aluminum alloys or aluminum-containing metal prepared by reacting bauxite at a high temperature with a reducing agent, such as coke or carbon.

Carbothermic aluminum alloys contain a minor or major amount of aluminum and might have the following composition.

Component: Percent by weight Aluminum 40-70 Iron -45 Silicon 2-20 Titanium 2-6 Carbon 3-6 Manganese Less than 3 Aluminum alloys having the above composition can be treated for the recovery of relatively pure aluminum therefrom. One method employed for the production of relatively pure aluminum from aluminum alloys, such as carbothermic aluminum alloys having a composition described hereinabove, involves contacting the aluminum alloy, usually particle-form aluminum alloy, at a high temperature, such as a temperature in the range 1000- 140()o C., more or less, and at a suitable pressure, such as subatmospheric, atmospheric or superatmospheric pressure, in the range 5-1560 mm. Hg absolute with a gaseous aluminum trihalide. On high temperature contact of the aluminum alloy which the gaseous aluminum trihalide chemical reaction occurs with the formation of gaseous aluminum monohalide. The thus-formed gaseous aluminum-monohalide is separately recovered and treated for the formation of substantially pure aluminum therefrom.

The method usually employed for the production of substantially pure aluminum from a gaseous monohalide involves cooling or condensation of the gaseous monohalide to` eect disproportionation thereof to yield elemental aluminum in substantially pure form which is recovered as product and gaseous aluminum trihalide which is recovered and advantageously recycled to contact additional aluminum alloy.

The above-described process for the recovery of substantially pure aluminum from aluminum alloys by reaction with an aluminum trihalide is sometimes referred to as the subhalide distillation or catalytic distillation of aluminum.

In the preparation of substantially pure aluminum from aluminum alloys by high temperature treatment With a gaseous aluminum trihalide, other materials or metals present in the aluminum alloy undergoing treatamaai Patented June 16, 1964 ice ment tend to react with the aluminum trihalide treating agent to form corresponding halides which also tend to be distilled with the aluminum monochloride and to be eventually recovered in the elemental aluminum produced as product.

Manganese is an example of a metal frequently found associated with aluminum in carbothermic aluminum l alloys. Manganese, when present admixed with aluminum in an aluminum-containing alloy undergoing treatment by reaction with an aluminum trihalide for the production ofsubstantiallypure aluminum, tends to distill or be removed as a manganese halide, manganese subnalide, together with the aluminum monohalide. Accordingly, upon subsequent treatment of the aluminum monohalide to produce elemental aluminum, elemental manganese is also produced with the aluminum. As a result the produced elemental aluminum is contaminated or contains a substantial amount of elemental manganese.

Accordingly, it is an object of this invention to provide an improved process for the manufacture of substantially pure aluminum.

It is another object of this invention to provide an improved process for the manufacture of substantially manganese-free aluminum from a manganese-containing aluminum alloy.

Still another object of this invention is to provide an improved process for the manufacture of substantially pure aluminum from carbothermic aluminum alloys.

Yet another object of this invention is to provide an improved subhalide distillation or 'catalytic distillation process for the recovery of substantially pure aluminum from aluminum alloys containing admixed therewith metals which tend to concomitantly distill with the aluminum and be recovered therewith.

How these and other objects of this invention are achieved will become apparent in the light of the accompanying disclosure made with reference to the accompanying drawing wherein there is schematically illustrated allow scheme in accordance with one embodiment of the practices of this invention for the production of substantially manganese-free aluminum from a manganese-containing aluminum alloy.

In accordance with this invention substantially pure aluminum is obtainable from an aluminum alloy, such as a carbothermic aluminum alloy, e.g. a manganese-containing cmbothermic aluminum alloy, by countercurrently contacting a body of mass of said aluminum alloy, preferably a mass of particle-form aluminum alloy, with a gaseous aluminum trihalide under conditions to effect reaction between the aluminum in said alloy and the gaseous aluminum trihalide to form the corresponding gaseous aluminum monohalide.

The above contacting-reaction operation is carried out cyclicly, preferably employing a downward moving bed or mass of particle-form aluminum alloy within a vertically disposed contactor-roactcr or converter. During each complete operation or cycle the contactor-reactor is charged withl fresh aluminum alloy and the contacting operation employing hot gaseous aluminum trihalide is continued until there appears in the gaseous eliiuent from the contactor-reactor aluminum monohalide together with a predetermined amount of other metal halide, eg. manganese subhalide. During the cycle the gaseous eiuent containing substantially only aluminum monohalide initially recovered from the contacter-reactor is directed to a condenser or decomposer wherein the'temperature of the gaseous aluminum monohalide-containing effluent is reduced, such as to a temperature substantially below the operating temperature employed in the contaeter-reactor.

When the gaseous aluminum monohalide-containing effluent is cooled to a suitable lower temperature, eg. about 700 C., disproportionation of the aluminum monohalide occurs with the formation of substantially pure elemental aluminum and gaseous aluminum trihalide. The thus-produced gaseous aluminum trihalide is advantageously recovered and returned to the contacter-reactor to contact the aluminum alloy therein. Further, during each complete cycle in accordance with the practice of this invention when the amount of other metal halides, eg. manganese subhalide, appears in the gaseous effluent above a predetermined concentration, or to an undesirable extent, the gaseous effluent from the contactor-reactor is separately recovered and treated to produce therefrom elemental aluminum containing said other metal or metals admixed therewith. During this portion of the complete cycle the feed of fresh aluminum alloy to the contactorreactor is preferably discontinued and the Withdrawal of spent alloy from the contacter-reactor is also preferably discontinued.

The introduction of the gaseous aluminum trihalide into the contacter-reactor is continued, however, under conditions to effectively strip all of the aluminum from the aluminum alloy within the contactor-reactor, together with said other metals which react with the aluminum trihalide to form halides which concomitantly distill and are carried away in the resulting gaseous eiuent from the contactor-reactor together with the aluminum monohalide. Following this stripping operation for the removal of substantially all of the aluminum from the aluminum alloy within the contactor-reactor, the remaining alloy therein is discharged from the contactor-reactor and the contactor-reactor charged with fresh aluminum alloy and the above-described operations or cycle repeated.

It is thus seen in accordance with this invention that the gaseous effluent containing aluminum monohalide is separated into two portions, a first or initial portion which is recovered during the active refining operation and which upon cooling decomposes to yield substantially pure elemental aluminum and a second portion recovered during the stripping operation and which upon cooling decomposes to yield elemental aluminum admixed with another metal, such as manganese.

Further explanatory of the practices of this invention, during the treatment of aluminum alloy with an aluminum trihalide, such as aluminum trichloride, for the preparation of substantially pure aluminum therefrom, certain metals, particularly manganese, are carried over with the aluminum and contaminate the resulting aluminum product. During the initial stages of the contacting operation wherein a mass of manganese-containing aluminum alloy is countercurrently contacted with a gaseous aluminum trihalide the aluminum recovered as product from the first or initial gaseous effluent is substantially pure Whereas the aluminum recovered as product from the subsequent or second gaseous effluent contains a substantially higher proportion of manganese than originally present in the feed aluminum alloy charged to the contactor-reactor. Accordingly, in a batch operation wherein substantially all of the aluminum is extracted from a given amount of aluminum alloy charged to the contacter-reactor, substantially all of the manganese or other equivalent metal contaminants therein are also extracted. In a straightforward batch operation wherein all the gaseous eiiiuent is recovered without segregation the original ratio of aluminum to metal contaminants in the alloy, such as the original aluminum to manganese ratio, will also be found in the aluminum recovered as product.

In the practice of this invention a mass of particleform aluminum alloy containing a metal contaminant, e.g. manganese, which tends to be removed with the aluminum, is subjected to direct counter-current contact with a gaseous trihalide under conditions such that the gaseous aluminum trihalide contacts fresh aluminum alloy just before it is withdrawn as gaseous effluent from the contaeter-reactor. This Contact with the fresh aluminum alloy tends to rectify the gaseous eiuent just before it leaves the contacter-reactor and tends to remove any metal contaminant, such as manganese, therefrom. It is seen, however, that in such an operation the metal contaminant, manganese, does not leave the contactor-reactor with the gaseous effluent or with the spent alloy but rather the metal contaminant, manganese, tends to accumulate in the middle section or portion of the contactor-reactor. The accumulation of metal contaminant, manganese, in the aluminum alloy within the contactorreactor continues until the aluminum alloy therein becomes so enriched with respect to the metal contaminant, manganese, that the incoming fresh aluminum alloy feed can no longer satisfactorily rectify and remove the metal contaminant, manganese, from the gaseous eiuent leaving the contacter-reactor without passing on to the gaseous effluent the ratio of aluminum to metal contaminant, manganese, in the alloy which is in equilibrium with the gaseous effluent. Accordingly, when such a point is reached and the contacting-reaction operation continued, the eventual result with respect to the purity of the produced aluminum will be the same as that obtainable in a batch operation without segregation of the gaseous eiiiuent, i.e. the aluminum to metal contaminant (manganese) ratio will be the same in the product distillate as in the charge alloy.

This condition is avoided in accordance with the practices of this invention. When the aluminum to metal contaminant, manganese, ratio in the gaseous efHuent and/or in the resulting produced refined aluminum reaches a predetermined level, the gaseous eiuent issuing from the contacter-reactor is then separately recovered and treated for the recovery of the aluminum, the aluminum previously recovered from the gaseous effluent being recovered as substantially pure aluminum product. At this point desirably the feed of fresh aluminum alloy into the contactor-reactor is discontinued and the Withdrawal of the spent aluminum alloy from the contactorreactor is also discontinued. The introduction of gaseous aluminum trihalide, however, into the contacter-reactor is continued during this stripping operation until substantially all of the aluminum from the aluminum alloy Within the contactor-reactor is removed in the gaseous effluent together with any of the metal contaminant, manganese, which distills or is removed therewith. Following the stripping of substantially all of the aluminum from the aluminum alloy within the contactor-reactor the spent aluminum alloy is discharged and the contactorreactor charged with fresh aluminum alloy and the aforesaid operations repeated.

By carrying out these operations in accordance with this invention it is possible to effect, in the case of manganese, about a 10:1 enrichment of the metal contaminant, manganese, in the aluminum all-oy within the contactor-reactor, Accordingly, out of every l0() pounds of manganese-containing aluminum alloy supplied to the contactor-reactor it should be possible by following the practices of this invention to produce about pounds of substantially manganese-free aluminum and about l0 pounds of manganese-containing aluminum alloy.

Reference is now made to the accompanying drawing which schematically illustrates one embodiment of the practices of this invention directed to the refining of a manganese-containing aluminum alloy, such as a manganeso-containing carbothermic aluminum alloy, by the subhalide distillation or catalytic distillation process employing gaseous aluminum trichloride as the reactant aluminum trihalide. As illustrated therein a vertically disposed elongated converter or contacter-reactor 10 is provided substantially filled with a mass of particle-form manganese-containing aluminum alloy 11. Hot, gaseous aluminum trichloride is introduced via line 12 into the lower portion of contactor-reactor and resulting gaseous effluent is recovered from the upper portion of contaeter-reactor 10 via line 14. Fresh particle-form aluminum alloy is supplied from hopper via conduit 16 and star valve 18 into the top portion of contactor-reactor 1@ and spent, substantially aluminum-free alloy is discharged from the lower portion of contacter-reactor 1t) via star valve 19, conduit 2li into car or vessel 21 for further treatment or disposal as desired.

In the initial operation of contacter-reactor 1t) hot, gaseous aluminum trichloride is continuously introduced thereinto via line 12 and fresh aluminum alloy is supplied to the upper portion thereof from hopper 15 via conduit 16 and star valve 1S and spent alloy is discharged from the lower portion or bottom of contactor-reactor 1@ via star valve 19 and conduit Ztl. The mass 12 of particle-form aluminum alloy within contacter-reactor 16 is maintained therein at a suitable elevated temperature, such as a temperature in the range l000-1400 C., effective to carry out the reaction between the gaseous aluminum trichloride and the aluminum in the aluminumcontaining alloy to yield aluminum monochloride in accordance with the chemical equation:

The resulting formed aluminum monochloride is removed as gaseous effluent from the upper portion of contactor-reactor 1l) via line 14. The gaseous aluminum monochloride just prior to leaving the contactor-reactor 1@ via line 14 contacts the fresh aluminum alloy feed being supplied to the upper portion of contactor-reactor 1li The resulting formed manganese subhalide or manganese dichloride (MnCl2) tends to be stripped or removed from the gaseous eluent withdrawn from the upper portion of contacter-reactor 1i? as it contacts additional fresh aluminum alloy feed in the upper portion of contaeter-reactor 1G.

in accordance with this invention gaseous aluminum trichloride is continuously introduced via line 12 into contactor-reactor 1li and particle-form manganese-containing aluminum alloy is supplied to the upper portion of contacter-reactor 1G via star valve 18 and spent aluminum alloy, substantially free of aluminum, is withdrawn from the lower portion of contactor-reactor 1@ via star valve 19. initially, the gaseous eluent comprising substantially only aluminum monochloride is continuously withdrawn from the upper portion of contacterreactor 1 via line 14 and supplied via line 22 through open valve 22a into condenser-decomposer 24 wherein the temperature of the gaseous efuent is reduced to a suitable value, at least about 200 degrees centigrade below that of the operating temperature within contactorreactor 1G. Usually, satisfactory results are obtained by maintaining or operating condenser-decomposer 24 at an elevated temperature just above the melting point ot aluminum, 660 C., such as a temperaturein the range 70D-900 C., so that the gaseous aluminum monochloride introduced thereinto via line 22 undergoes disproportionation to form substantially pure molten aluminum and aluminum trichloride in accordance with the chemical equation:

Since the gaseous effluent supplied to condenser-decomposer 24 via lines 14 and 22 comprises substantially only gaseous aluminum mono'chloride together with some unreacted aluminum trichloride, the molten aluminum recovered as product from condenser-decomposer 24 via line 25 comprises substantially only pure aluminum. The unreacted aluminum trichloride, together with the aluminum trichloride formed during the disproportionation reaction, is withdrawn from the upper portion of condenser-decomposer 24 via line 26. Advantageously, the aluminum trichloride thus withdrawn from condenser-de- Composer 25 is returned to contactor-reactor 10 Via line 12 to contact additional aluminum alloy therein.

After a period of time the gaseous eflluent withdrawn via line 14 from the upper portion of contactor-reactor 10 will evidence increasing amounts of metal contaminants, such as manganese, as the concentration ork proportion of these metal contaminants, particularly manganese, increases within the central portion or middle section of the downwardly moving mass 11 of aluminum alloy within contacter-reactor 19. Withdrawal of the gaseous etlluent from the upper portion of Vcontactor-reactor itl via lines 14- and 22 to condenser-decomposer 24 for the production of substantially pure product aluminum is containued until the proportion or concentration of metal contaminant such as manganese Within the gaseous eluent in line 14 reaches an undesirable level and/ or until the amount of metal contaminants within the aluminum withdrawn from condenser-decomposer 24 via line 25 reaches a predetermined value.

When such a condition exists, valve 22a in line 22 is closed and valve 23a in line 28 is opened. The gaseous effluent issuing from contacter-reactor 10 via line 14 is then transferred via line 28 through valve 28a into condenser-decomposer 29 maintained under temperature conditions similar to those maintained in condenser-decomposer 24. The gaseous eluent comprises aluminum monochloride and metal contaminant, such as manganese dichloride, supplied via line 28 to condenser-decomposer 29 is subjected to temperature conditions therein such that the aluminum monochloride undergoes disproportionation to yield metallic aluminum and aluminum trichloride and the manganese dichloride reacts with the aluminum monochloride to form metallic manganese and aluminum trichloride in accordance With the chemical equation:

MnClg-l-AlCleMn-l-AICIS There is withdrawn from condenser-decomposer 29 via line 3] a contaminated stream of metallic aluminum, such as manganese-aluminum alloy, e.g. aluminum alloy containing about 3%, more or less, by weight manganese. The aluminum alloy removed Vfrom condenserdecomposer 29 via line 30 is recovered as. product or may be subjected to an additional treatment employing the practices of this invention for the production of substantially pure aluminum. The aluminum trichloride formed within condenser-decomposer 29 is withdrawn from the upper portion thereof via yline 31. Advantageously, this aluminum trichloride is returned via line 12 to contacter-reactor 10 tocontact additional aluminum alloy therein. Y

During the period of operation wherein the gaseous aluminum monochloride-containing euent is recovered from the upper portion of contacter-reactor 1l) and supplied via lines 12 and 28 to condenser-decomposer 29, the withdrawal of spent alloy in the lower portion of contactor-reactor 1G is substantially or completely stopped and the introduction offeed particle-form aluminum alloy in the upper portion of contacter-reactor 11B via conduit 16 and star valve 18 is also substantially or completely stopped.

The introduction of aluminum trichloride into the lower portion of contactor-reactor 1) and the Withdrawal of resulting gaseous effluent from 'the upper portion of contactor-reactor 11i via lines 14 and 28 into condenserdecomposer 29 is lcontinued until substantially all of the aluminum Within the aluminum alloy within contactorreactor 10 has been depleted or removed so that the residual alloy Within contactor-reactor l is substantially free or contains but a minor, relatively unimportant, amount of aluminum. When this condition obtains the remaining alloy within contactor-reactor 16 is discharged via star valve 19 and conduit 20 and carried away via car or vessel 2l for further treatment and recovery of metal values therefrom, as desired. Upon discharge of the remaining spent aluminum alloy from contacter-reactor .10 charge particle-form aluminum alloy is introduced into contactor-reactor l0 from hopper 15 via conduit i6 and star valve 18 to form an additional mass of aluminum alloy for treatment therein.

The above-described cycle of operations in accordance with this invention is then commenced again, i.e. gaseous aluminum trichloride introduced via line i4 into contactor-reactor while fresh feed particle-form aluminum alloy is added thereto through star valve 18 and spent aluminum alloy withdrawn via star valve 19 and conduit 20 as the charged particle-form aluminum alloy substantially continuously descends as a downwardly moving mass within contactor-reactor l0 and in continuous direct countercurrent contact with an upwardly flowing stream of gaseous aluminum trichloride,

In the practice of this invention in accordance with the embodiment illustrated in the drawing two separate condenser-decomposers are employed, condenser-decomposer 24 being employed for 'the production and recovery of substantially pure aluminum and condenser-decomposer 29 being employed for the production of metal-contaminated aluminum alloy, such as manganese-aluminum alloy. If desired, a single condenser-decomposer may be employed in connection with all the operations in the complete cycle of this invention, the single condenserdecomposer being employed for 'the production and recovery of substantially pure aluminum and, subsequently, for the production and recovery of metal-contaminated aluminum, such as manganese-aluminum alloy. When but a single condenser-decomposer is employed the condenser-decomposer is emptied so as to be free of pure aluminum prior to the admission thereinto of the gaseous eiiluent contaminated with another metal. Also, instead of two, three or any suitable number of condenser-decomposers may be employed in combination with one or a plurality of contactor-reactors, particularly when it may be desired to recover as product a very pure aluminum or aluminum having varying amounts of metal contaminants therein.

The following is exemplary of the practices of this invention. There is provided a vertically disposed contactor-reactor substantially of the type illustrated in the accompanying drawing and having a charge capacity of about 1000 lbs. of fresh aluminum alloy, such as a carbothermic manganese-containing aluminum alloy. The contactor-reactor may be considered as comprising six sections or zones numbered 1 through 6 from the top down. Zone 1 of the contacter-reactor would contain 100 pounds of feed alloy, zones 2, 3, 4 and 5, respectively, 200 pounds of feed alloy each and zone 6 at the bottom 100 pounds of feed alloy. The feed alloy supplied thereto would contain 56% by weight aluminum and 0.2% manganese, the remainder being iron and other contaminants, such as silicon, titanium and carbon. In the treatment of this aluminum alloy in accordance with this invention it is desired to produce a substantially pure aluminum product containing not more than 0.05% by weight manganese.

At 0.05% manganese in the gaseous effluent from the contactor-reactor the ratio of aluminum to manganese in the manganese-aluminum alloy is approximately 100. This means that under operating conditions so as to yield 0.05% manganese in 'the contactor-reactor gaseous eflluent the manganese content in the aluminum alloy within Zone l must be 0.56%.

The accompanying Table I shows the conditions of zones 1 through 6 of the contactor-reactor initially in the practice of this invention and at that .point of the operation at which the manganese content in the gaseous eiuent from the contactor-reactor has risen to 0.05%.

TABLE I Initial Final Zone - Wt. Percent Per- Per- Wt. Percent Per- Per- Allo Extraccent cent lb. Extraccent cent lb. tion A1 Mn tion Al Mn From the above ligures it is seen that the contactorreactor will have produced 1920 pounds of 0.03% magnesium-aluminum alloy as distillate and that the stripping of the residual alloy Within the contactor-reac'tor at this point in accordance with the practice of this invention will yield 280 pounds of 3% magnesium-containing aluminum, It is thus seen that 87% of the total aluminum recovered as product is substantially manganese-free or low manganese content aluminum.

Further illustrative of the practices of this invention, this time employing a vertically disposed elongated contactor-reactor having a charge capacity of 5 tons of particle-form aluminum alloy, the charged contactor-reactor is heated by suitable means, such as by passing a current of electricity therethrough or by means of suitable electrical resistance elements, to about 12.00 C. Thereupon, hot, gaseous aluminum trichloride is introduced into the bottom of the converter to pass into direct countercurrent contact with the charge aluminum alloy therein, fresh aluminium alloy being continuously added to the upper portion of the contactor-reactor and spent aluminum alloy being substantially continuously withdrawn from the lower portion of the contactor-reactor. The gaseous elnent issuing from the upper portion of the contacter-reactor is passed to a condenser-decomposer and the aluminum recovered therefrom.

These operations are continued until analysis shows that the manganese to aluminum ratio in the gaseous efiluent issuing from the contactor-reactor has reached a predetermined high level. When this predetermined level of manganese in the gaseous eluent is reached, the gaseous efliuent is diverted to another condenser-decomposer. Alternatively, the condenser decomposer in use may be drained of substantially al1 of the aluminum metal and the operations then continued therewith. Preferably at the same time the addition of fresh feed alloy to the contactor-reactor is halted and the withdrawal of spent aluminum alloy also halted or reduced to a very low level. The introduction of gaseous aluminum trichloride into the contactor-reactor, however, is continued as initially and the heat required to effect reaction between the aluminum trichloride and the aluminum in the alloy within the contactor-reactor is supplied as required. A continuously decreasing amount of heat will be necessary at this stage of the operation. During this period of operation, the socalled stripping period, manganese-rich aluminum alloy is collected in the condenser-decomposer and the aluminum alloy in the contacter-reactor is stripped of aluminum and manganese.

When the aluminum monochloride concentration in the gaseous effluent from the contactor-reactor and the manganese to aluminum ratio therein fall to a suihcie-ntly low level the addition of fresh aluminum alloy and the removal of spent alloy from the contacter-reactor are resumed and, desirably, the rate of introduction of gaseous aluminum trichloride into the contactor-reactor is temporarily reduced. The flow of gaseous eiuent from the contacter-reactor is then diverted to the original condenser-decomposer, or alternatively, the decomposer is once again drained of metal. When the stripped alloy has been removed from the contactor-reactor the rate of introduction of gaseous aluminum trichloride in the contaeter-reactor is raised to its initial value and the aforesaid cycle of operations repeated.

The following examples demonstrate the results obtainable when the practice of this invention is carried out as described hereinabove:

Example N o. 1

An alloy containing 56% aluminum, 2.7% silicon and 0.2% manganese (the balance being iron, titanium, carbon and minor constituents), is treated in the described manner. Refining is continued until removal of 95% of the aluminum from the alloy is achieved. When the manganese to aluminum ratio in the gas increases to 0.0012 the converter or contactor-reactor gas is diverted. During this initial part of the operation 10.75 tons of aluminum containing 0.028% manganese is collected. After diversion, 1 ton of aluminum containing 3.82% manganese is collected before feed aluminum alloy additions to the converter are recommenced and the gas is rediverted.

Example No. 2

The same alloy is treated, but diversion is not undertaken until the manganese to aluminum ratio is 0.0013. Under these conditions 11.2 tons of aluminum containing 0.033% manganese, and 1 ton of aluminum containing 3.93% manganese, are separately collected in each cycle.

Example N0. 3

Using the alloy of Example No. 1 refining is limited to removal of 90% of the aluminum therefrom. The diversion of gas from the converter is undertaken when the manganese to aluminum ratio in the gas increases to 0.00115. Before diversion 11.1 tons of aluminum containing 0.029% manganese is collected, and before rediversion 1 ton of aluminum containing 4.05% manganese is collected.

Example No. 4

Using an alloy similar to that of Example No. 1, except that the manganese content is 0.05%, refining is continued until removal of 95% of the aluminum from the alloy is achieved. Diversion is carried out when the manganese to aluminum ratio increases to 0.0008. Before diversion 45 tons of aluminum containing 0.01% manganese is collected, and before rediversion 1 ton containing 3.84% manganese is obtained.

Example No. 5

An alloy similar to that of Example No. 1, but with a manganese content of 1.0% is refined to 95 removal of the aluminum. When the manganese to aluminum ratio is 0.0187 the gas is diverted. A total of 9.5 tons of aluminum containing 1.5% manganese is collected in the initial phase of the cycle, and 1 ton of 4.55% manganese metal in the second phase.

Example No. 6

An alloy similar to that of Example No. 1, except that lthe silicon content is 6.0%, is refined to 95 removal of the aluminum. The gas is diverted when the manganese to aluminum ratio reaches 0.00125. Under these conditions 11.25 tons of 0.0296% manganese, and 1 ton of 4.12% manganese, metal are produced in the two phases of each cycle of operation.

Although in the foregoing description of the invention the terms converter and contacter-reactor have been used interchangeably, in industry the term converter is used, and is preferred, to refer to the apparatus wherein hot gaseous aluminum trihalide contacts the aluminumcontaining metal to effect reaction therebetween with the introducing an aluminum-containing alloy into a contacting-reaction zone, said alloy also containing relatively minor amounts of other metals as contaminants, at least one of said other metals being capable ofreacting with an aluminum trihalide to form a vaporizable metal halide, contacting said alloy in said contacting-reaction zone with a hot `gaseous aluminum trihalide at a temperatureV in the range 1000-1400 C. to react the aluminum in said alloy and the gaseous aluminum trihalide to form a gaseous aluminum monohalide, withdrawing from the contactingreaction zone an initial gaseous effluent containing aluminum monohalide and recovering substantially pure aluminum therefrom, continuing the introduction of said alloy into said contacting-reaction zone, the withdrawal of said initial gaseous eflluent and discharging spent alloy from said contacting-reaction zone having a substantially reduced aluminum content during the aforesaid contactingreaction operation until the concentration of the metalcontaminant in the alloy within the contacting-reaction zone is increased to a level such that the concentration .of the metal-contaminant halide in said initial gaseous elhuent withdrawn from the contacting-reaction Zone increases to an undesirable predeterminel level, thereupon discontinuing the introduction of said alloy into said contacting-reaction zone and the discharge of said spent alloy therefrom, subsequently stripping aluminum and at least a portion of said other metal contaminants from said alloy remaining in said contacting-reaction zone by contacting said remaining alloy with additional hot gaseous aluminum trihalide, withdrawing a second gaseous eiuent from said contacting-reaction zone lseparately from said initial gaseous effluent and separately recovering aluminum from said second gaseous eilluent contaminated with the aforesaid metal contaminant.

2. A method in accordance with, claim l wherein particle-form alloy is introduced into said contacting-reaction zone.

3..A method in accordance with claim 1 wherein said aluminum trihalide is aluminum trichloride.

4. A method in accordance with claim 1 wherein one of said other metals present in said alloy is manganese.

5. A method in accordance with claim 1 wherein said aluminum-containing alloy contains at least 35% by weight aluminum.

6. A method in accordance with claim 1 wherein said contacting-reaction zone is an elongated vertically-extending zone and wherein said alloy is introduced thereinto countercurrently with respect to said gaseous aluminum trihalide.

7. A method in accordance with claim 1 wherein said contacting-reaction zone is an elongated vertical zone, said alloy being introduced at one end thereof and said gaseous aluminum trihalide being introduced into the other end thereof, the initial and second effluents from said contacting-reaction zone being withdrawn therefrom at about said one end thereof.

8. A method in accordance with claim 1 wherein said aluminum-containing alloy is a carbothermic aluminum alloy produced by the reduction of bauxite.

9.v A method in accordance with claim 1 wherein the initial gaseous eiuent withdrawn from the contactingreaction zone prior to the stripping operation is reduced in temperature to eiect disproportationation of the aluminum monohalide therein to recover the substantially pure aluminum and aluminum trihalide.

10. A method in accordance with claim 1 wherein said aluminum trihalide produced by the disproportionation of the aluminum monohalide is returned to the contacting-reaction zone to Contact additional aluminum alloy.

11. A method in accordance with claim 1 wherein said aluminum alloy comprises a major amount of aluminum and a minor amount, below about 3% by Weight, manganese.

UNITED STATES PATENTS Cleaves Aug. 7, 1917 Frost Aug. 15, 1933 Frost Nov. 13, 1934 Gross May 17, 1949 Loevensten July 4, 1950 Gross Aug. 19, 1952 Pedersen et al Dec. 9, 1952 Phillips et al. Nov. 15, 1955 Milliken Nov. 19, 1957 Johnston et al. May 17, 1960 Hollingshead Feb. 19, 1963 

1. A METHOD OF REFINING ALUMINUM WHICH COMPRISES INTRODUCING AN ALUMINUM-CONTAINING ALLOY INTO A CONTACTING-REACTION ZONE, SAID ALLOY ALSO CONTAINING RELATIVELY MINOR AMOUNTS OF OTHER METALS AS CONTAMINANTS, AT LEAST ONE OF SAID OTHER METTALS BEING CAPABLE OF REACTING WITH AN ALUMINUM TRIHALIDE TO FORM A VAPORIZABLE METAL HALIDE, CONTACTING SAID ALLY IN SAID CONTACTING-REACTION ZONE WITH A HOT GASEOUSS ALUMINUM TRIHALIDE AT A TEMPERATURE IN THE RANGE 1000-1400*C. TO REACT THE ALUMINUM IN SAID ALLOY AND THE GASEOUS ALUMINUM TRIHALIDE TO FORM A GASEOUS ALUMINUM MONOHALIDE, WITHDRAWING FROM THE CONTACTINGREACTION ZONE AN INITIAL GASEOUS EFFLUENT CONTAINING ALUMINUM MONOHALIDE AND RECOVERING SUBSTANTIALLY PURE ALUMINUM THEREFROM, CONTAINING THE INTRODUCTION OF SAID ALLOY INTO SAID CONTACTING-REACTION ZONE, THE WITHDRAWL OF SAID INITIAL GASEOUS EFFLUENT AND DISCHARGING SPENT ALLOY FROM SAID CONTACTING-REACTION ZONE HAVING A SUBSTANTIALLY REDUCED ALUMINUM CONTENT DURING THE AFORESAID CONTACTINGREACTION OPERAION UNTIL THE CONCENTRATION OF THE METALCONTAMINANT IN THE ALLOY WITHIN THE CONTACTING-REACTION ZONE IS INCREASED TO A LEVEL SUCH THAT THE CONCENTRATION OF THE METAL-CONTAMINANT HALIDE IN SAID INITIAL GASEOUS EFFLUENT WITHDRAWN FROM THE CONTRACTING-REACTION ZONE INCREASES TO AN UNDESIRABLE PREDETERMINEL LEVEL, THEREUPON DISCONTINUING THE INTRODUCTION OF SAID ALLOY INTO SAID CONTRACTING REACTION ZONE AND THE DISCHARGE OF SAID SPENT ALLOY THEREFROM, SUBSEQUENTLY STRIPPING ALUMINUM AND AT LEAST A PORTION OF SAID OTHER METTAL CONTAMINANTS FROM SAID ALLOY REMAINING IN SAID CONTACTING-REACTION ZONE BY CONTACTING SAID REMAINING ALLOY WITH ADDITIONAL HOT GASEOUS ALUMINUM TRIHALIDE, WITHDRRAWING A SECOND GASEOUS EFFLUENT FROM SAID CONTACTING-REACTION ZONE SEPARATELY FROM SAID INITIAL GASEOUS EFFLUENT AND SEPARATELY RECOVERING ALUMINUM FROM SAID SECOND GASEOUS EFFLUENT CONTAMINATED WITH THE AFORESAID METAL CONTAMINANT. 